1. Field of the Invention
This invention is directed to tongs; in one aspect to a power tong with two or more floating jaws; and in other aspects to a floating tong jaw and other parts of a tong, e.g., a jaw urging system.
2. Description of Related Art
A variety of operations related to drilling a wellbore and to producing oil and other fluids from it involve the threaded connection of tubular members such as casing, drill pipe, tubing or sucker rods. The prior art discloses numerous power operated tongs that are used to impart rotational torque to one tubular to threadedly connect it with another tubular. One type of power tong uses jaws which move into contact with a tubular to grip it. Rotation of a member to which the jaws are connected or with which the jaws co-act results in rotation of the tubular which has been gripped by the jaws. Elementary mechanisms for the transfer of rotative force to a tubular are described in U.S. Pat. No. 4,346,629, co-owned with this application.
One type of prior art power tong has a body, a rotary rotatably mounted in said body, and at least one active jaw which, on rotation of the rotary, is cammed against a cam surface of a cam member which moves the jaw into contact with a pipe which has been positioned in the rotary. The jaw contacts the pipe and grips it for rotation with the rotary.
The camming action is generated by the cam member which is bolted to the rotary and is shaped so that the active jaw will be cammed against the pipe on rotation of the rotary relative to the active jaw in one direction and will be released on rotation of the rotary relative to the active jaw in the opposite direction. In order to reverse the screwing direction of the tong with one active jaw, the active jaw is removed and remounted on the opposite side of the rotary. On rotation of the rotary relative to the active jaw in the opposite direction, the active jaw is cammed against the pipe by a second cam member. This is a time-consuming process and the tong must be removed from the pipe to enable the active jaw to be moved.
One prior art power tong, T, is depicted in FIGS. 1-3. The tong T has a fixed master jaw M pinned to an inner ring, R, and an active jaw, A, also pinned to the inner ring R. The jaws are rotated and activated by the combined action of a rotary gear, G, a brake (not shown) and the cam rollers, C. During makeup operations, a pipe to be turned is first enclosed in the tong and a tong door (not shown) is closed. Then, with the jaws in the makeup position, a control lever is pulled causing the jaws to bite and rotate the pipe. To release the jaws and back off from the pipe, the tong control lever is again moved (e.g., inwardly). During breakout operations, the jaws are placed in the breakout position so that the jaws bite in the reverse direction. The tong control lever is pushed, causing the jaws to bite and rotate the pipe. Finally, the control lever is pulled to release the jaws and back them off the pipe.
As shown in FIGS. 1-3 the jaw-biting action is the result of the rotary gear-cam rollers/jaw-cam surface interaction. When the rotary gear rotates, the rollers roll up onto the jaw cam surface and force the jaws to bite the pipe. Further rotation turns the pipe to make up or break out a joint. To provide the restraint necessary for camming to occur, a brake is applied. The brake induces drag on the inner ring within the tong sufficient to permit the jaw roller to push the jaw into engagement with the pipe. Once the jaw is engaged and power to the rotary is increased, the brake is overcome, allowing the jaws to rotate with the rotary gear.
In order to reverse the direction of the tong T shown in FIGS. 1-3, openings in the rotary and tong body must first be aligned. Then the pins are unscrewed and removed from the master jaw and from the active jaw. The jaws are removed from the inner ring, inverted, and re-positioned on the inner ring. Once the pins are replaced the tong is ready for use in the opposite direction. Typically this takes several minutes for one reversal of direction. This prior art tong and its operation are described in the manual submitted herewith entitled "Model 4.5-08 Hydraulic Power Tong, Weatherford Power Equipment" and in the brochure entitled "Model 4.5 Hydraulic Power Tong." (co-owned with this invention).
Prior art U.S. Pat. No. 5,044,232, co-owned with this application, discloses another tong with a slidable passive jaw and an active jaw. The active jaw has dual cam member surfaces which co-act with rollers to move the active jaw into and out of contact with a pipe. The active jaw is held in place on a jaw assembly by the dual cam members and by a spring which urges the jaw against the rollers. To reverse the direction of this tong a bolt is moved in a slot of the drum that carries the active jaw until it contacts a surface in the rotary. The active jaw does not need to be removed.
Prior art U.S. Pat. No. 5,380,323 discloses a power tong having a housing, an annular rotor carried by the housing, reversible drive means for rotating the rotor in either direction,
jaw means mounted on the rotor in such a manner as to permit limited rotation of the rotor relative to the jaw means in either direction, double-acting cam means for closing the jaw means in response to limited rotation of the rotor relative to the jaw means in either direction from a neutral position, braking means for restraining the jaw means upon rotation of the rotor in either direction to actuate the cam means and thus close the jaw means, and spring means for biasing the jaw means open in opposition to the action of the cam means so that the jaw means opens when it is in its neutral position relative to the rotor. The housing, the rotor and the jaw means have registerable radial throats permitting radial insertion of a pipe or rod starting into the jaw means into a position to be gripped by the jaw means upon closing thereof. The double-acting cam means closes the jaw means in response to rotation of the rotor in either direction, as long as the braking means restrains the jaw means in order to permit the rotor to rotate relative to the jaw means in either direction the relative neutral positions of the rotor and the jaw means. The jaws are diametrically opposed and have cam follower rollers mounted on the jaws. The jaws are guided by guide walls on the rotor. A leaf spring urges the jaws against the cam surfaces on the rotor.
There has long been a need for a tong with active jaws which can be easily and efficiently reversed in direction. There has long been a need for such a tong which applies evenly distributed loads to a tubular member. There has long been a need for an effective and efficient floating jaw urging system.